Aluminum bronze alloy having improved wear resistance by the addition of cobalt and chromium



V r 2,944,890 "ALUMINUM BRONZE ALLOY HAVING IM- 'PROVED WEAR RESISTANCEBY THE AD- DITION'OF COBALT AND CHROMIUM John Klemen't, Milwaukee, Wis,assignor to Ampco .Metal, Inc., Milwaukee, Wis., a corporation of WIS-consin 4 No Drawing. Filed Jan. 22, 1958, Ser. No. 710,*4l0

5 Claims. (Cl. 75--162) The aluminum bronze alloys which in the pasthave shown the optimum properties for deep drawing dies are those thatcontain approximately 14% aluminum, a small amount of iron and thebalance copper. An alloy of this type has good corrosion resistance andnon-galling properties. However, under, heavy use in die application, itwears undesirably fast so that close dimensional tolerances cannot bemaintained because of the wear that occurs on the diesurface. H

The present invention is directed to an aluminum bronze alloy which hasthe corrosion resistance and the nongalling properties characteristic ofaluminum bronze alloys ice The above alloy can becast either staticallyor'centrifugally to produce a fine grained tough structure having, inthe chilled cast state, a tensile strength of 100,000 p.s.i., a yieldstrength of 75,000 p.s.i., an elongation in two inches of 1.5% and aRockwell C hardness of 40.

The alloy of the invention has greatly improved wear resistance overthat of an ordinary aluminum bronze alloy and this increase in wearresistance is most significant since the hardness of the alloy issubstantially the same as the hardness of an aluminum bronze alloyhaving similar proportions of aluminum and iron but not containing thecobalt and chromium. For example, the wear resistance of the presentalloy is about 50% to 80% better than the conventional aluminum bronzealloy, the toughness is 100% to 150% better, and the machinability, atthe lower chromium contents, is about 100% better I than the ordinaryaluminum bronze alloy not containing the cobalt and chromium.

The metallographic structure of the alloy consists essentially of gammatwo phase which is uniformly distributed in a matrix of beta. Anintermediate compound composed of iron, aluminum, copper, cobalt andchromium exists in small particles of uniform size and shape. Because ofthe method of casting and the inoculant used, the intermetallic compoundis uniformly distributed throughout the cast section.

In order to obtain optimum properties, the metals used for the alloyshould be of high quality. Electrolytic .or wrought fire refined copper,high purity aluminum, low carbon iron and high purity cobalt andchromium are preferred to be used. It has also been found that the bestmethod of obtaining the desired uniformity in the alloy is by using adouble meltinglprocedure whereby a prealloy is made. The .mostsatisfactory pre-alloy is one that has 10% chromium and 10% cobalt.

but has greatly improved wear resistance and toughness.

alloy is suchthat some copper, along with the iron,

The aluminum bronze alloy of the invention has high uniform hardness,goodtoughness'a'nd excellent wear resistance. This is accomplished bythe addition of small amounts of cobalt and chromium to the alloy whichsubstantially reduces the tendency of the alloy to form the eutectoid.The addition of cobalt and chromium also makes the alloymore-homogeneous in the distribution of the metallurgical phases andcompounds during solidification and heat treatment and also promotesuniform controlled grain size.

Furthermore, the alloy, particularly at the. lower end of the chromiumrange, has a' finer and rounder'particle size than the ordinary aluminumbronze alloy which resultsin better machinability. p

The alloy of the invention has thefollowing general composition byweight:

This alloy has a tensile strength of about 65,000 to 105,000 p.s.i., ayield strength of 65,000 to 80,000 p.s.i., an elongation in two inchesof up to 2.5% and a Rockwell C hardness in the range of 25 to 55.

A specific illustration of the composition of the alloy falling withinthe above range. is as follows in weight percent:

. Percent Aluminum 15.10 Iron 5.01 Cobalt 3.18

' Chromium 1.50

Copper 73.93

The melting procedure employed in making the pre- The final alloy ismade by intermixing a predetermined percentage of the pre-alloy andcopper. A deoxidizer is added to this alloy in the molten state in thefurnace to purge the metal of oxides and soluble gases. Thesedeoxidizers can include the compounds of boron, phosphorus, magnesiumand lithium. Deoxidizers of the gas type can also be used. This caninclude volatile chlorides or any of the inert gases. The dry typedeoxidizers are added in quantities of approximately 4 ounces per poundsof metal, and the gas type deoxidizers are passed either through or overthe molten metal for a period of five minutes. Removal of'the oxideparticles is of particular importance because of their abrasive andadverse effect on the wear-resistant properties of the alloy.

Alternately, instead of employing a pre-alloy, the chromium and cobaltcan be added directly to a molten aluminum-iron-copper alloy.

To establish complete uniformity of the microstru ture and hardness thealloy is heat treated at an elevated temperature, in the temperaturerange, of 1050 F. to 1400" F such as about 1150 F. Small castings ofsimple shapes of this alloy' can be placed directly into the heattreating furnace at temperature. Large massive castings or intricateshapes are preheated in the furnace at about 400 F. until the sectionreaches uniform temperature and then are heated directly to the elevatedtemperature.

Patented July 12, 1960 3 The castings are held at a temperature in therange of 1050F. to 1400 F. for one hour plus one-half hour 20 F. perhour per one inch vof section thickness. This.

rate is conveniently obtained by fan air cooling.

Internal stresses created within castings during machining or otherfinishing operations, during Weldments or from metal overlays on basemetals, are usually removed depending on the future application of thepart. These stresses are removed by astress relief heat treatment.cannot generally be stress relieved at a temperature in the range of 650F. to 1050 F. due to eutectoid formation that occurs at this temperaturerange. stress relief at temperatures above 1050 F. frequently causesdistortions and further stresses in the usual commercial aluminum bronzealloy during the rapid cooling to room temperature. Stress relief attemperatures lower than 650 F. takes considerable time and often the'most severe stresses remain. V

In contrast to this, the alloy of the invention can be stress relievedwithin the temperature range of 650 F to 1050 F. without excessiveembrittlement due to the eutectoid structure. An optimum stress relieftemperature for the present alloy, based on the severity of the internalstresses and geometry of the article, can be selected in the range of650 F. to 1050 F. to obtain a reasonable holding time in the furnace,such as one to two hours per 2 inches of section, and to preventdistortions and micro stresses during cooling. The article is Thearticles may take the form of deep drawing dies,

The usual commercial aluminum bronze alloys- Furthermore, a

Various nodes of carrying out the invention are eontemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim: I

1.-An aluminum bronze alloy, consisting essentially of 13.0% to 20.0%aluminum, from 1.0% to 8.0% iron, from 0.50% to 5.0% cobalt, from 0.5%to 3.0% chromium and the balance being substantially copper, said alloybeing characterized by having excellent corrosion resistance and havingimproved toughness and wear resistance.

2. An aluminum bronze alloy having improved wear resistance, toughnessand machinability, consisting essentially of from 13.0% to 20.0%aluminum, 1.0% to 8.0% iron, 0.5 to 5.0% ,cobalt,,0.5% to 3.0% chromiumand the balance substantially copper, said alloy being characterized bya tensile strength in the range of 65,000 to 105,000 p.s.i., a yieldstrength in the range of 65,000 to 80,000 p.s.i., an elongation in twoinches of up to 2.5%, and a hardness in the range of to 55 Rockwell C.

3. An aluminum bronze alloy having improved toughness and wearresistance, consisting essentially of 15.10%

' and 73.93% copper.

hold down dies, wear guides, forming rolls, skids, slides f etc.

The alloy can also be extruded into weldrods or weld Wire. The alloyin'the form of coated ,or uncoated weldrod can be overlaid on a basemetal by metal spray.-

ing or other welding methods,;such as heli-arc, metal-arc,

carbon-arc, etc. to obtain a corrosion resistant wear 'surface. Themetal overlay can be given a stress relief treat-v ment at temperaturesin the range of 650 F. to 1150 F.

As the alloy of the- 4. A drawing die characterized by having excellentcorrosion resistance, a hardness in the range of 25 to Rockwell C. andimproved wear resistance, said die being fabricated from an aluminumbronze alloy .consisting essentially of 13% to 20% aluminum, from 1% to8% iron, from 0.5% to 5% cobalt, from 1% to 3% chromium, and the balancebeing substantially copper.

5. An aluminum bronze welding electrode consisting essentially of 13% to20% aluminum, from 1% to 8% iron, from 0.5% to 5% cobalt, from 1.0% 'to3.0% chromium, and the balance being substantially copper.

. References Cited in the file of this patent UNITED STATES PATENTS2,789,900

'1 2,809,139 Bloom et a1. Oct. -8, 1957 2,829,971 'Klement -Apr. 8, 19582,829,972 5 Klement "Apr. 8, 1958 2,832,709 Sendzimir Apr. 29, 1958FOREIGN PATENTS Great Britain June 20, 1941 OTHER REFERENCES Non-FerrousTubes in'the Stress of Modern Conditions, Breckon et al., MetalIndustry, August 1, 1958, pages 89-90.

Ellis: Copper and Copper Alloys ,(AmericanSociety for. Metals, 1948),pages 1 62170. Aluminum Bronze (London: Copper Development Association,1939), pages 45-50.

Hannon Apr. 23, 1957'

1. AN ALUMINUM BRONZE ALLOY, CONSISTING ESSENTIALLY OF 3.0% TO 20.0%ALUMINUM, FROM 1.0% TO 8.0% IRON, FROM 0.50% TO 5.0% COBALT, FROM 0.5%TO 3.0% CHROMIUM AND THE BALANCE BEING SUBSTANTIALLY COPPER, SAID ALLOYBEING CHARACTERIZED BY HAVING EXCELLENT CORROSION RESISTANCE AND HAVINGIMPROVED TOUGHNESS AND WEAR RESISTANCE.